Thread: copying and ball jigs cutting without tearing

I know. I know. This seems to be the only things I reply to. Carbide cutting tools and copy lathes. Unless it is a monster sized turning or something out of the ordinary. Carbide CAN achieve just as fine a cutting edge as HSS. Most comments to the contrary are based on improper sharpening techniques and dated information. Many times people purchase the wrong edge prep on an insert and blame the tool for being dull, to stand up to metal turning the dull edge is intentional! There is a hone dimention to the edge of the insert. which is a flat area at the edge. Inserts ground for aluminum on the other hand often are ground "sharp No hone" I have used carbide tooling since the '70's for certain applications and find them very usefull. here is a shot of carbide tooling doing the job. Sanding is minimal.

As for copy lathes and there use: cutting edge grind and presentation make all the difference. some of the home made duplicators use a flat top scraper type cutter with a sharp point which will surly leave you with a 60 grit finish at best. If the tool was sharpened with side and top relief it would self feed and catch. sharpened with top relief only will burnish the wood and leads to a lot of sanding as well. Ball jigs allow good solid control of the tool but can still self feed. As far as only cutting down hill for a good finish again that comes down to being able to properly control the cutting edge. By hand cutting down hill one can shear cut because you "push the cut" the bevel rides on material that has been cut already to stabilize it. To go up hill the bevel has to ride material that will be cut so in order to do that the cutting edge must be opened up, the tool self feeds and you have a catch or at best an uneven feed which causes raged grain and lots of sanding. that is why scrapers are used by many turners to finish cut the inside of bowls they don't self feed and are very controllable. Automatic lathes cut from one end to the other with a good finish both up and down hill. There are two types single pass 1,2 and three cutter, and the single pass 1 and 2 cutter back knife lathe Full profile shaper lathes don't count do they ? lol. It all comes down to cutter geometry,edge prep, presentation and control. Here is a vid of a single point coy lathe in action cutting both down hill and up hill with a very acceptable off the tool finish. Most have seen this before.


Here is a reverse ball turning jig lol I use it fir the inside of production bowls